Vehicle occupant detection systems are useful in connection with air bags and other pyrotechnically deployed restraints as a means of judging whether, and how forcefully, to deploy the restraint. One fundamental parameter in this regard is the weight of the occupant, as weight may be used as a criteria to distinguish between an adult and an infant or small child.
One prior weight estimation technique is to install an array of variable resistance pressure sensitive elements in the seat, and to sum the individual pressures to determine occupant weight. A restraint system based on this technique is shown and described in the U.S. Pat. No. 5,474,327, issued on Dec. 12, 1995, and assigned to the assignee of the present invention. In practice, however, such systems tend to be relatively costly to implement, and require a significant amount of signal processing for proper calibration and weight estimation.
Another technique, described in U.S. Ser. No. 08/801,218, entitled Adaptive Seating System, filed on Feb. 19, 1997, pending, and assigned to General Motors Corporation, involves measuring and adjusting the pressure in several inflated bladders variously located in a given passenger seat. When a sharp increase in the measured pressures is detected, the passenger weight is estimated based on a comparison of current pressures with previously measured "vacant seat" pressures.
Also, designers of seating, athletic shoes and the like have utilized a technique in which a large number of small bladders distributed throughout the area of interest are individually and sequentially evacuated and then filled with a known volume of air. Pressure readings from each bladder are stored and used to create a pressure distribution map.